Big problems come in small particles – how micropollutants affect water supply

Posted 9 May 2018

From pharmaceutical products washed down the drain to pesticides, herbicides hormones and nanoparticles, there are multiple hazardous contaminants making their way into water streams – and it’s a major global issue.

The presence of micropollutants in our water has seen the emergence of pollutant-removal technologies across the world, and according to Arup Process Engineer Gabrielle Butera at Ozwater’18, technology needs to stay one step ahead of the issue if health and environments are to be safeguarded.

“The chemical properties of emerging contaminants mean that conventional wastewater treatment is often inadequate in removing these compounds,” Butera said.

“An understanding of priority emerging contaminants is required in addition to a knowledge of innovative and developing technologies for their treatment or removal.”

A review of monitoring and investigation programs of relevant authorities in the UK, US, Europe and Australia established a shortlist of 10 key priority contaminants that have the potential to or are already, affecting the environment.

According to Butera, by establishing these priority contaminants, emerging treatments could be developed to target them specifically – with the most widely-used method for monitoring such contaminants at present being spot sampling and laboratory chemical analysis through gas chromatography-mass spectrometry (GC-MS).

Butera said that at the moment, conventional treatment for drinking water and municipal wastewater were found to be inadequate in the removal of all 10 compounds, and while various innovative treatment options have been investigated showed promising results for the removal of several contaminants, the processes are still in research and development.

PFAS problems

Hunter H2O Principal Scientist Dr Yaode Yan, who spoke about the options and challenges in the removal of PFAS from drinking water supply, said with instances of PFAS groundwater contamination blossoming around Australia’s RAAF sites, councils and water utilities are becoming more vigilant about their source water quality.

While PFAS removal will lead to significant increases in the cost of water treatment, handling of the PFAS-containing residual is by no means a lesser challenge, he said.

“PFAS chemicals are very persistent. They are highly resistant to physical, chemical or biological degradation. And they are so widespread, it could potentially end up being a huge problem,” Yan said.

While the health effects to humans from PFAS exposure may be inconclusive at this stage, Yan said the resilience and ubiquitousness of PFAS heightens the risks associated with leaving them unaddressed.

Yan said commercially viable methods for drinking water treatment are currently limited to the use of activated carbon, anion exchange, nanofiltration or reverse osmosis.

“Unfortunately, all treatment methods create waste, either solid or liquid, and when the waste is PFAS rich, what can we do about it?” he said.

“It is really a challenge dealing with PFAS-containing residuals in Australia. We can readily establish treatment facilities to remove PFAS from the water supply, but we are faced with the uncertainty of what to do with a concentrated PFAS waste stream.”

Stockpiling of PFAS-containing wastes is not a long-term solution, according to Yan, but added that these challenges also offer the opportunity for Australia to become leaders in PFAS waste management.

“If you look nationally, the country’s first PFAS National Environmental Management Plan was released in February 2018. It provides a nationally consistent approach to the environmental regulation of PFAS,” Yan said. “Australia is certainly taking the issue very seriously.”

Do we have to worry about engineered nanomaterials next?

Chemical engineer Ian Law raised the concern that engineered nanomaterials (ENMs) are being increasingly used in many industrial sectors worldwide, which will bring with it an increased presence of these materials in municipal wastewaters, and ultimately, community water sources and supplies.

Law said, when combined with the roll out of potable reuse schemes, as traditional water resources decline, a major problem emerges – a growing need to develop capabilities to measure the risk-potential posted by ENMs now and into the future.

“The use of ENMs in the electronics, energy, cosmetics, medical, defence, food and agriculture industries is on the increase,” Law said.

“Research work in Europe, the US, Australia, Singapore and China shows ENMs are now present in the environment and could also be present in drinking water after conventional treatment.”

Ingestion of ENMs could cause adverse health effects related to elevated levels of metal concentrations in livers, kidneys, the brain and bloodstream, as studies with rats and mice has proven.

“The presence of ENMs in the environment implies their passage through wastewater treatment plants (WWTP),” Law said.

“This fact highlights the importance of the robustness of the Source Control Program (SCP) and the design of the WWTP, these being the first two barriers in any reuse scheme and the main barriers for discharges of treated effluent to the environment.”

According to Law, the way forward includes a “coordinated effort” in Australia from universities, water utilities, water sector companies and research institutions to address the issue now, rather than wait until the community raises the issue and questions the safety of the water supply.

“The aim of this coordinated effort should be to improve the evidence base of information on key ENMs from a public health risk standpoint. We need to know if we have a looming problem, particularly as the ENM industry continues to grow and new ENM products enter our space and end up in our wastewaters.”

Ozwater’18 is currently ongoing in Brisbane, at the Brisbane Convention and Exhibition Centre, from now until 10 May.